1
|
Petkowski JJ, Seager S, Grinspoon DH, Bains W, Ranjan S, Rimmer PB, Buchanan WP, Agrawal R, Mogul R, Carr CE. Astrobiological Potential of Venus Atmosphere Chemical Anomalies and Other Unexplained Cloud Properties. ASTROBIOLOGY 2024; 24:343-370. [PMID: 38452176 DOI: 10.1089/ast.2022.0060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/09/2024]
Abstract
Long-standing unexplained Venus atmosphere observations and chemical anomalies point to unknown chemistry but also leave room for the possibility of life. The unexplained observations include several gases out of thermodynamic equilibrium (e.g., tens of ppm O2, the possible presence of PH3 and NH3, SO2 and H2O vertical abundance profiles), an unknown composition of large, lower cloud particles, and the "unknown absorber(s)." Here we first review relevant properties of the venusian atmosphere and then describe the atmospheric chemical anomalies and how they motivate future astrobiology missions to Venus.
Collapse
Affiliation(s)
- Janusz J Petkowski
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Faculty of Environmental Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland
- JJ Scientific, Mazowieckie, Warsaw, Poland
| | - Sara Seager
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | | | - William Bains
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- School of Physics and Astronomy, Cardiff University, Cardiff, UK
| | - Sukrit Ranjan
- Lunar and Planetary Laboratory, Department of Planetary Sciences, University of Arizona, Tucson, Arizona, USA
| | - Paul B Rimmer
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Weston P Buchanan
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana, USA
| | - Rachana Agrawal
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Rakesh Mogul
- California Polytechnic University, Pomona, California, USA
| | - Christopher E Carr
- School of Aerospace Engineering and School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| |
Collapse
|
2
|
Mogul R, Avice G, Limaye S, Way M. Deriving new mixing ratios for Venus atmospheric gases using data from the Pioneer Venus Large Probe Neutral Mass Spectrometer. MethodsX 2023; 11:102305. [PMID: 37577164 PMCID: PMC10415784 DOI: 10.1016/j.mex.2023.102305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 07/28/2023] [Indexed: 08/15/2023] Open
Abstract
We present the first published method to convert data obtained by the Pioneer Venus Large Probe Neutral Mass Spectrometer (LNMS) into units of mixing ratio (ppm) and volume percent (v%) against CO2 and N2, the dominant Venus atmospheric gases, including conversion to density (kg m-3). These unit conversions are key to unlocking the untapped potential of the data, which represents a significant challenge given the scant calibration data in the literature. Herein, we show that our data treatments and conversions yield mixing ratios and volume percent values for H2O, N2, and SO2 that are within error to those reported for the gas chromatograph (LGC) on the Pioneer Venus Large Probe (PVLP). For the noble gases, we developed strategies to correct for instrument biases by treating the data as a relative scale and using PVLP and Venera-based measurements as calibration points. Together, these methods, conversions, calibrations, and comparisons afford novel unit conversions for the LNMS data and yield unified measures for Venus' atmosphere from the LNMS and LGC on the PVLP.•Conversion into mixing ratio (ppm), volume percent (v%), and density (kg m-3).•Mixing ratios are expressed against CO2 and N2.•LNMS and LGC measurements on the PVLP are consistent.
Collapse
Affiliation(s)
- R. Mogul
- Chemistry & Biochemistry Department, California State Polytechnic University, Pomona, CA, USA
- Blue Marble Institute of Science, Seattle, WA USA
| | - G. Avice
- Université Paris Cité, Institut de physique du globe de Paris, CNRS, Paris, F-75005, France
| | - S.S. Limaye
- Space Science and Engineering Center, University of Wisconsin, Madison, WI, USA
| | - M.J. Way
- NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY, USA
- GSFC Sellers Exoplanet Environments Collaboration, Greenbelt, MD, USA
- Theoretical Astrophysics, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
| |
Collapse
|
3
|
Warren AO, Kite ES. Narrow range of early habitable Venus scenarios permitted by modeling of oxygen loss and radiogenic argon degassing. Proc Natl Acad Sci U S A 2023; 120:e2209751120. [PMID: 36877840 PMCID: PMC10089166 DOI: 10.1073/pnas.2209751120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Accepted: 01/13/2023] [Indexed: 03/08/2023] Open
Abstract
Whether Venus was ever habitable is a key question driving missions to Earth's sister planet in the next decade. Venus today has a dry, O2-poor atmosphere, but recent work has proposed that early Venus may have had liquid water [J. Krissansen-Totton, J. J. Fortney, F. Nimmo, Planet. Sci. J. 2, 216 (2021)] and reflective clouds that could have sustained habitable conditions until 0.7 Ga [J. Yang, G. Boué, D. C. Fabrycky, D. S. Abbot, Astrophys. J. 787, L2 (2014), M. J. Way, A. D. Del Genio, J. Geophys. Res.: Planets 125, e2019JE006276 (2020)]. Water present at the end of a habitable era must since have been lost by photodissociation and H escape, causing buildup of atmospheric oxygen [F. Tian, Earth Planet. Sci. Lett. 432, 126-132 (2015)]. We present a time-dependent model of Venus's atmospheric composition starting from the end of a hypothetical habitable era with surface liquid water. We find that O2 loss to space, oxidation of reduced atmospheric species, oxidation of lava, and oxidation of a surface magma layer formed in a runaway greenhouse climate can remove O2 from up to 500 m global equivalent layer (GEL) (30% of an Earth ocean), unless melts on Venus had a much lower oxygen fugacity than Mid Ocean Ridge melts on Earth, which increases the upper limit twofold. Volcanism is required to supply oxidizable fresh basalt and reduced gases to the atmosphere but also contributes 40Ar. Consistency with Venus's modern atmospheric composition occurs in less than 0.4% of runs, in a narrow parameter range where the reducing power introduced by O2 loss processes can balance O2 introduced by H escape. Our models favor hypothetical habitable eras ending before 3 Ga and very reduced melt oxygen fugacities three log units below the fayalite-magnetite-quartz buffer (fO2< FMQ-3), among other constraints.
Collapse
Affiliation(s)
| | - Edwin S. Kite
- Department of Geophysical Sciences, University of Chicago, Chicago, IL60637
| |
Collapse
|
4
|
Production of ammonia makes Venusian clouds habitable and explains observed cloud-level chemical anomalies. Proc Natl Acad Sci U S A 2021; 118:2110889118. [PMID: 34930842 PMCID: PMC8719887 DOI: 10.1073/pnas.2110889118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/11/2021] [Indexed: 11/18/2022] Open
Abstract
This research provides a transformative hypothesis for the chemistry of the atmospheric cloud layers of Venus while reconciling decades-long atmosphere anomalies. Our model predicts that the clouds are not entirely made of sulfuric acid, but are partially composed of ammonium salt slurries, which may be the result of biological production of ammonia in cloud droplets. As a result, the clouds are no more acidic than some extreme terrestrial environments that harbor life. Life could be making its own environment on Venus. The model’s predictions for the abundance of gases in Venus’ atmosphere match observation better than any previous model, and are readily testable. The atmosphere of Venus remains mysterious, with many outstanding chemical connundra. These include the unexpected presence of ∼10 ppm O2 in the cloud layers, an unknown composition of large particles in the lower cloud layers, and hard to explain measured vertical abundance profiles of SO2 and H2O. We propose a hypothesis for the chemistry in the clouds that largely addresses all of the above anomalies. We include ammonia (NH3), a key component that has been tentatively detected both by the Venera 8 and Pioneer Venus probes. NH3 dissolves in some of the sulfuric acid cloud droplets, effectively neutralizing the acid and trapping dissolved SO2 as ammonium sulfite salts. This trapping of SO2 in the clouds, together with the release of SO2 below the clouds as the droplets settle out to higher temperatures, explains the vertical SO2 abundance anomaly. A consequence of the presence of NH3 is that some Venus cloud droplets must be semisolid ammonium salt slurries, with a pH of ∼1, which matches Earth acidophile environments, rather than concentrated sulfuric acid. The source of NH3 is unknown but could involve biological production; if so, then the most energy-efficient NH3-producing reaction also creates O2, explaining the detection of O2 in the cloud layers. Our model therefore predicts that the clouds are more habitable than previously thought, and may be inhabited. Unlike prior atmospheric models, ours does not require forced chemical constraints to match the data. Our hypothesis, guided by existing observations, can be tested by new Venus in situ measurements.
Collapse
|
5
|
Limaye SS, Mogul R, Baines KH, Bullock MA, Cockell C, Cutts JA, Gentry DM, Grinspoon DH, Head JW, Jessup KL, Kompanichenko V, Lee YJ, Mathies R, Milojevic T, Pertzborn RA, Rothschild L, Sasaki S, Schulze-Makuch D, Smith DJ, Way MJ. Venus, an Astrobiology Target. ASTROBIOLOGY 2021; 21:1163-1185. [PMID: 33970019 DOI: 10.1089/ast.2020.2268] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We present a case for the exploration of Venus as an astrobiology target-(1) investigations focused on the likelihood that liquid water existed on the surface in the past, leading to the potential for the origin and evolution of life, (2) investigations into the potential for habitable zones within Venus' present-day clouds and Venus-like exo atmospheres, (3) theoretical investigations into how active aerobiology may impact the radiative energy balance of Venus' clouds and Venus-like atmospheres, and (4) application of these investigative approaches toward better understanding the atmospheric dynamics and habitability of exoplanets. The proximity of Venus to Earth, guidance for exoplanet habitability investigations, and access to the potential cloud habitable layer and surface for prolonged in situ extended measurements together make the planet a very attractive target for near term astrobiological exploration.
Collapse
Affiliation(s)
- Sanjay S Limaye
- Space Science and Engineering Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Rakesh Mogul
- Chemistry and Biochemistry Department, Cal Poly Pomona, Pomona, California, USA
| | - Kevin H Baines
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | | | - Charles Cockell
- School of Physics and Astronomy, University of Edinburgh, Edinburgh, Scotland
| | - James A Cutts
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Diana M Gentry
- NASA Ames Research Center, Moffett Field, California, USA
| | | | - James W Head
- Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island, USA
| | | | - Vladimir Kompanichenko
- Institute for Complex Analysis of Regional Problems, Russian Academy of Sciences, Birobidzhan, Russia
| | - Yeon Joo Lee
- Zentrum für Astronomie und Astrophysik, Technical University of Berlin, Berlin, Germany
| | - Richard Mathies
- Chemistry Department and Space Sciences Lab, University of California, Berkeley, Berkeley, California, USA
| | - Tetyana Milojevic
- Department of Biophysical Chemistry, University of Vienna, Vienna, Austria
| | - Rosalyn A Pertzborn
- Space Science and Engineering Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | | | - Satoshi Sasaki
- School of Health Sciences, Tokyo University of Technology, Hachioji, Japan
| | - Dirk Schulze-Makuch
- Center for Astronomy and Astrophysics (ZAA), Technische Universität Berlin, Berlin, Germany
- German Research Centre for Geosciences (GFZ), Potsdam, Germany
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Stechlin, Germany
| | - David J Smith
- NASA Ames Research Center, Moffett Field, California, USA
| | - Michael J Way
- NASA Goddard Institute for Space Studies, New York, New York, USA
| |
Collapse
|
6
|
Mogul R, Limaye SS, Lee YJ, Pasillas M. Potential for Phototrophy in Venus' Clouds. ASTROBIOLOGY 2021; 21:1237-1249. [PMID: 34569810 DOI: 10.1089/ast.2021.0032] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We show that solar irradiances calculated across Venus' clouds support the potential for Earth-like phototrophy and that treatment of Venus' aerosols containing neutralized sulfuric acid favor a habitable zone. The phototrophic potential of Venus' atmosphere was assessed by calculating irradiances (200-2000 nm, 15° solar zenith angle, local noon) using a radiative transfer model that accounted for absorption and scattering by the major and minor atmospheric constituents. Comparisons to Earth's surface (46 W m-2, 280-400 nm) suggest that Venus' middle and lower clouds receive ∼87% less normalized UV flux (6-7 W m-2) across 200-400 nm, yet similar normalized photon flux densities (∼4400-6200 μmol m-2 s-1) across 350-1200 nm. Further, Venus' signature phototrophic windows and subwindows overlap with the absorption profiles of several photosynthetic pigments, especially bacteriochlorophyll b from intact cells and phycocyanin. Therefore, Venus' light, with limited UV flux in the middle and lower clouds, is likely quite favorable for phototrophy. We additionally present interpretations to refractive index and radio occultation measures for Venus' aerosols that suggest the presence of lower sulfuric abundances and/or neutralized forms of sulfuric acid, such as ammonium bisulfate. Under these considerations, the aerosols in Venus' middle clouds could harbor water activities (≥0.6) and buffered acidities (Hammett acidity factor, H0 -0.1 to -1.5) that lie within the limits of acidic cultivation (≥H0 -0.4) and are tantalizingly close to the limits of oxygenic photosynthesis (≥H0 0.1). Together, these photophysical and chemical considerations support a potential for phototrophy in Venus' clouds.
Collapse
Affiliation(s)
- Rakesh Mogul
- Chemistry & Biochemistry Department, California State Polytechnic University, Pomona, California, USA
| | - Sanjay S Limaye
- Space Science and Engineering Center, University of Wisconsin, Madison, Wisconsin, USA
| | - Yeon Joo Lee
- Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Berlin, Germany
| | - Michael Pasillas
- Chemistry & Biochemistry Department, California State Polytechnic University, Pomona, California, USA
| |
Collapse
|
7
|
Mogul R, Limaye SS, Way MJ, Cordova JA. Venus' Mass Spectra Show Signs of Disequilibria in the Middle Clouds. GEOPHYSICAL RESEARCH LETTERS 2021; 48:e2020GL091327. [PMID: 34219837 PMCID: PMC8244101 DOI: 10.1029/2020gl091327] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 02/08/2021] [Accepted: 03/02/2021] [Indexed: 05/11/2023]
Abstract
We present a re-examination of mass spectral data obtained from the Pioneer Venus Large Probe Neutral Mass Spectrometer. Our interpretations of differing trace chemical species are suggestive of redox disequilibria in Venus' middle clouds. Assignments to the data (at 51.3 km) include phosphine, hydrogen sulfide, nitrous acid, nitric acid, carbon monoxide, hydrochloric acid, hydrogen cyanide, ethane, and potentially ammonia, chlorous acid, and several tentative PxOy species. All parent ions were predicated upon assignment of corresponding fragmentation products, isotopologues, and atomic species. The data reveal parent ions at varying oxidation states, implying the presence of reducing power in the clouds, and illuminating the potential for chemistries yet to be discovered. When considering the hypothetical habitability of Venus' clouds, the assignments reveal a potential signature of anaerobic phosphorus metabolism (phosphine), an electron donor for anoxygenic photosynthesis (nitrite), and major constituents of the nitrogen cycle (nitrate, nitrite, ammonia, and N2).
Collapse
Affiliation(s)
- Rakesh Mogul
- Chemistry & Biochemistry DepartmentCalifornia State Polytechnic University, PomonaPomonaCAUSA
- Blue Marble Space Institute of ScienceSeattleWAUSA
| | | | - M. J. Way
- Department of Physics and Astronomy, Theoretical AstrophysicsUppsala UniversityUppsalaSweden
- Laboratory of GeneticsUniversity of WisconsinMadisonWIUSA
- NASA Goddard Institute for Space StudiesNew YorkNYUSA
| | - Jaime A. Cordova
- Space Science and Engineering CenterUniversity of WisconsinMadisonWIUSA
| |
Collapse
|
8
|
Schulze-Makuch D. The Case (or Not) for Life in the Venusian Clouds. Life (Basel) 2021; 11:255. [PMID: 33804625 PMCID: PMC8003671 DOI: 10.3390/life11030255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Revised: 03/16/2021] [Accepted: 03/17/2021] [Indexed: 01/04/2023] Open
Abstract
The possible detection of the biomarker of phosphine as reported by Greaves et al. in the Venusian atmosphere stirred much excitement in the astrobiology community. While many in the community are adamant that the environmental conditions in the Venusian atmosphere are too extreme for life to exist, others point to the claimed detection of a convincing biomarker, the conjecture that early Venus was doubtlessly habitable, and any Venusian life might have adapted by natural selection to the harsh conditions in the Venusian clouds after the surface became uninhabitable. Here, I first briefly characterize the environmental conditions in the lower Venusian atmosphere and outline what challenges a biosphere would face to thrive there, and how some of these obstacles for life could possibly have been overcome. Then, I discuss the significance of the possible detection of phosphine and what it means (and does not mean) and provide an assessment on whether life may exist in the temperate cloud layer of the Venusian atmosphere or not.
Collapse
Affiliation(s)
- Dirk Schulze-Makuch
- Astrobiology Research Group, Center for Astronomy and Astrophysics (ZAA), Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany; ; Tel.: +49-30-314-23736
- German Research Centre for Geosciences (GFZ), Section Geomicrobiology, 14473 Potsdam, Germany
- Department of Experimental Limnology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, (IGB), 12587 Stechlin, Germany
- School of the Environment, Washington State University, Pullman, WA 99163, USA
| |
Collapse
|